docs: def remote_bifurcation_angle(bif_point):
      '''Return the opening angle between two out-going sections
      in a bifurcation point
  
      We first ensure that the input point has only two children.
  
      The angle is defined as between the bifurcation point and the
      last points in the out-going sections.
      '''
      assert len(bif_point.children) == 2, 'A bifurcation point must have exactly 2 children'
  
      return morphmath.angle_3points(bif_point.points[-1],
                                     bif_point.children[0].points[-1],
                                     bif_point.children[1].points[-1])